This practice covers general recommendations for photoelectric photometers and spectrometers and for photometric practice for chemical analysis of metals, ores, and related materials. However, this practice does not include a description of every apparatus nor does it present recommendations on every detail of practice in photometric or spectrophotometric methods of chemical analysis of metals. To improve photoelectric photometers and spectrophotometers, some suggestions related to their components are mentioned, in particular, the radiation source (illuminant), filters, monochromators, absorption cells, photosensitive tubes, and current-measuring devices. In addition, prior to using photometric methods in the chemical analysis of metals, ores, and related materials, it is recommended that a complete photometric investigation of the reaction be performed. The investigation shall involve the study of the specificity of the reagent used to produce absorption; validity of Beer's law; effects of salts, solvent, pH, temperature, concentration of reagents, and the order of adding reagents; time required for absorption development and the stability of the absorption; absorption curve of the reagent and the absorbing substances; and optimum concentration range for quantitative analysis.

1.1 This practice covers general recommendations for photoelectric photometers and spectrophotometers and for photometric practice prescribed in ASTM methods for chemical analysis of metals, sufficient to supplement adequately the ASTM methods. A summary of the fundamental theory and practice of photometry is given. No attempt has been made, however, to include in this practice a description of every apparatus or to present recommendations on every detail of practice in ASTM photometric or spectrophotometric methods of chemical analysis of metals.

1.2 These recommendations are intended to apply to the ASTM photometric and spectrophotometric methods for chemical analysis of metals when such standards make definite reference to this practice, as covered in Section 4.

1.3 In this practice, the terms "photometric" and "photometry" encompass both filter photometers and spectrophotometers, while "spectrophotometry" is reserved for spectrophotometers alone.

1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.